1. Field of the Invention
The invention relates to a control apparatus for an internal combustion engine. More particularly, the invention relates to a control apparatus for an internal combustion engine, which improves startability.
2. Description of the Related Art
Recently, a technology has been employed in a hybrid vehicle, an economical running vehicle, or the like, which automatically stops an engine, for example, while the vehicle stops and is in the idling state, and automatically restarts the engine when necessary, for example, at the time of take-off, whereby fuel efficiency is improved and exhaust gas is suppressed.
In a vehicle in which the engine is repeatedly stopped and started with frequency in the aforementioned manner, the internal combustion engine needs to be started smoothly with reliability. An example of a technology for enabling the internal combustion engine to start smoothly with reliability is disclosed in Japanese Patent Laid-Open Publication No. 2000-64874. In the technology disclosed in the patent publication, valve timing of an intake valve is delayed when a direct injection type engine starts, thereby reducing an effective compression ratio in a hybrid vehicle using a direct injection type engine and an electric motor. In the patent publication, it is described that the engine can be started smoothly while suppressing engine vibration, by reducing the effective compression ratio.
However, when the effective compression ratio is reduced, an output of the internal combustion engine is reduced, which makes it difficult to increase the output quickly. In the vehicle in which the engine is repeatedly stopped and started with frequency in the aforementioned manner, when the engine is started after it is stopped, for example, at the time of take-off or at the time of acceleration, a high output of the engine is often required, and accordingly, startability of the engine needs to be improved.